Data and R code from: GC-MS analysis of murine oestrous odours

For female mammals, communicating the timing of ovulation is essential for successful reproduction. Urinary volatile organic compounds (VOCs) play a key role in intraspecific communication among many mammals. Using laboratory mice as a model species, we investigated urinary VOCs across the oestrous cycle. We monitored the oestrous stage through daily vaginal cytology assessment and analysed urinary VOCs using headspace gas chromatography-mass spectrometry (GC-MS), testing the utility of portable GC-MS against the more robust benchtop device. We detected 65 VOCs from 40 samples stored in VOC traps and analysed on a benchtop GC-MS and 15 VOCs from 90 samples extracted by solid-phase microextraction (SPME) and analysed on a portable GC-MS. Only three of the identified compounds were found in common between the two techniques. Urine collected from the fertile stages of the oestrous cycle had increased quantities of a few notable VOCs (3,4-dehydro-exo-brevicomin, butanoic acid, pent-1-ene/cyclopentane, 1,2,3-/1,2,4-trimethylbenzene, heptadecane, dioctyl ether, dodecan-1-ol and 2-ethylhexyl salicylate), compared to urine collected from non-fertile stages. However, we did not find differences in the Bray-Curtis chemical dissimilarity indices among oestrous stages. It is possible that the variation in urine VOCs concentration at play during the oestrous cycle was too subtle to be detected by our analytical methods. Overall, the use of the VOC traps combined with benchtop GC-MS was more successful than SPME combined with portable GC-MS in capturing and identifying murine urinary VOCs. Nonetheless, portable GC-MS systems have the potential for some in situ applications since they allow for the immediate interpretation of results, especially at remote field sites.

Methods
Using laboratory mice as a model species, we investigated urinary VOCs across the oestrous cycle. We monitored the oestrous stage through daily vaginal cytology assessment and analysed urinary VOCs using headspace gas chromatography-mass spectrometry (GC-MS), testing the utility of portable GC-MS against the more robust benchtop device.

对于雌性哺乳动物而言，传递排卵时序信号是成功繁衍后代的关键前提。尿液挥发性有机化合物（volatile organic compounds，VOCs）在多数哺乳动物的种内通讯中发挥核心作用。本研究以实验小鼠为模式物种，对发情周期（oestrous cycle）内的尿液VOCs展开系统探究。研究人员通过每日阴道细胞学评估监测发情阶段，并采用顶空气相色谱-质谱联用法（headspace gas chromatography-mass spectrometry，GC-MS）分析尿液VOCs，同时对比便携式GC-MS与性能更稳定的台式设备的实用性。

研究从40份储存在VOC捕集管中并经台式GC-MS分析的样本中检出65种VOCs，同时从90份经固相微萃取（solid-phase microextraction，SPME）提取并通过便携式GC-MS分析的样本中检出15种VOCs。两种检测技术仅共有3种已鉴定的化合物。与非可育阶段采集的尿液相比，发情周期可育阶段的尿液中，数种特征性VOCs的含量显著升高，包括3,4-脱氢-外-brevicomin、丁酸、1-戊烯/环戊烷、1,2,3-/1,2,4-三甲基苯、十七烷、二辛基醚、1-十二烷醇以及水杨酸2-乙基己酯。但研究未发现不同发情阶段间的Bray-Curtis化学相异指数存在显著差异。这可能是因为发情周期内尿液VOCs浓度的变化过于细微，现有分析方法无法有效检出。总体而言，相较于SPME结合便携式GC-MS的方案，采用VOC捕集管联合台式GC-MS的方法在捕获并鉴定小鼠尿液VOCs方面效果更优。尽管如此，便携式GC-MS系统仍具备部分原位应用的潜力，因其可即时解析检测结果，尤其适用于偏远野外场地。

方法
以实验小鼠为模式物种，本研究对发情周期内的尿液VOCs展开探究。通过每日阴道细胞学评估监测发情阶段，并采用顶空气相色谱-质谱联用法（GC-MS）分析尿液VOCs，对比便携式GC-MS与性能更稳定的台式设备的实用性。